1. Field of the Invention
This invention pertains generally to circuit interrupters and, more particularly, to circuit breakers including a trip mechanism responsive to a plurality of different trip conditions.
2. Background Information
Circuit interrupters include, for example, circuit breakers, contactors, motor starters, motor controllers, other load controllers and receptacles having a trip mechanism. Circuit breakers are generally old and well known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 5,260,676; and 5,293,522.
Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. In small circuit breakers, commonly referred to as miniature circuit breakers, used for residential and light commercial applications, such protection is typically provided by a thermal-magnetic trip device. This trip device includes a bimetal which is heated and bends in response to a persistent overcurrent condition. The bimetal, in turn, unlatches a spring powered operating mechanism which opens the separable contacts of the circuit breaker to interrupt current flow in the protected power system. An armature, which is attracted by the sizable magnetic forces generated by a short circuit or fault, also unlatches, or trips, the operating mechanism.
In many applications, the miniature circuit breaker also provides ground fault protection. Typically, an electronic circuit detects leakage of current to ground and generates a ground fault trip signal. This trip signal energizes a shunt trip solenoid, which unlatches the operating mechanism, typically through actuation of the thermal-magnetic trip device. See, for example, U.S. Pat. Nos. 5,260,676; 5,293,522; and 5,982,593.
Also, in many applications, miniature circuit breakers provide arc fault protection. See, for example, U.S. Pat. Nos. 5,224,006; 5,691,869; and 5,982,593.
When the circuit breaker detects a potentially hazardous fault condition, it must open the protected power circuit as quickly as possible in order to interrupt the fault condition. There is a delay from the time that the circuit breaker electronic circuit issues a trip request to the time when the separable contacts actually sufficiently part and interrupt the fault condition. For example, this delay may be in the order of about one-half of a 60 Hz electrical cycle in a miniature circuit breaker. Also, when the separable contacts open, the circuit breaker electronic circuit is typically disconnected from its power source. There is typically sufficient energy storage in the circuit breaker power supply to sustain operation of the electronic circuit for about one-half of the 60 Hz electrical cycle after the separable contacts open.
Typically, faulty residential circuit breakers are returned to the manufacturer without any information regarding the current level, the cause-of-trip or the count of trips. For example, known returned arc fault/ground fault circuit breakers provide no information to the manufacturer as to whether the circuit breaker tripped for arc fault or ground fault conditions, and provide no information as to the current level at the time of tripping.
Accordingly, there is room for improvement in circuit interrupters and circuit breakers.